Method and apparatus for molding roofing products with back gating

ABSTRACT

A molding apparatus is configured with a distribution channel configured to deliver a blended feed composition directly into an article molding region such that a molded article is formed with gating on the bottom surface of the article. The article molding regions are formed into front sides of opposed “A” and “B” surface mold tools that, when moved into a mating relationship with one another, form closed molding cavities within which molded articles are generated from molding material feed. The article molding regions each generally have a body bounded by a perimeter that establishes an outer edge for an article molded in the one of the closed molding cavities. Additionally, the body of each article molding region of the “A” surface mold tool is adapted for molding a bottom surface for the composite article, and the body of the article molding region of the “B” surface mold tool is adapted for molding a top surface for the composite article. The distribution channel is formed in at least the second surface mold tool, and has a main portion and a downstream terminus for each article molding region of the “A” surface mold tool. The main portion of the distribution channel is formed outside of each article molding region. The downstream terminus, to which the main portion extends, is in communication with the body of the respective article molding region of the “A” surface mold tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority fromnonprovisional application Ser. No. 11/283,627, filed Nov. 21, 2005,entitled Method and Apparatus for Molding Roofing Products With BackGating. Application Ser. No. 11/283,627 is incorporated herein in itentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

Conventional injection molding processes have been modified to createcomposite building products that combine polymers with filler materials.For instance, composite shingles have been fabricated in a closedmolding process utilizing various combinations of polymers, such asrubber and thermoplastics (e.g., polyolefins, polyvinyl chloride, etc.)and fillers (e.g., glass, stone, limestone, talc, mica, cellulosicmaterials such as wood flour, rice hulls, etc.), along with colorants,and optionally, suitable UV inhibitors, lubricants and other additivesthat aid in the molding process and provide favorable physicalproperties to the finished composite shingles. Two popular types ofcomposite shingles formed in a closed molding process includingcomposite shake shingles and composite slate shingles. Different moldtools are created for each type of composite shingle, each with its ownsurface texturing or contouring to be imparted to the molded article.

A molding apparatus for creating composite building products generallyincludes opposed mold tools that combine to form one or more closedmolding cavities. While the mold tools are in contact with one anotherto form the cavities, one of the tools shapes a top surface of thecomposite building product, and the other tool shapes the bottom surfaceof the product. Additionally, one or both of the tools in cooperationshapes the side or outer edge of the composite building product.Typically, to deliver the material to be molded to the closed moldingcavities, a heated, flowable blended composition of a polymer and afiller is moved under pressure from a port in one or both of the opposedmolding tools to a distribution channel formed by the mating mold tools.The distribution channel is formed into the surfaces of the mold toolsthat face one another, in a similar fashion to the closed moldingcavities, and extends from the port to the article molding regions ofeach mold tool that form the closed molding cavities. More specifically,the distribution channel extends to a perimeter edge of each articlemolding region where the flowable composition is delivered into theclosed molding cavities. The composition is then cured in each cavityunder pressure for a sufficient period of time to form the moldedarticle as a composite building product. Subsequently, the mold toolsare separated and the molded articles removed.

The use of a distribution channel on the mold tool surfaces creates amolded gating waste piece that must be discarded. Because of thedistribution channel configuration, the gating piece extends from theside or outer edge of the molded article. Although removal of the gatingpiece from the molded article is generally not difficult, a vestige isleft behind as evidence that the gating piece was once attached to thearticle. This vestige is undesirable on either the side edge or the topsurface of the molded article, as these surfaces may remain exposedafter the composite building product is installed on a structural member(e.g., a composite shingle on a roof). It would be desirable to create acomposite building product free of a vestige or other mark that is aby-product of the molding process on the side edge or the top surface ofthe molded product.

SUMMARY OF THE INVENTION

A molding apparatus is provided for forming one or more molded articlesby delivering a blended feed composition to an article molding region sothat a gating piece is formed on the bottom surface of the moldedarticles. In this way, the exposed top surface and side edge of thearticle is free of a vestige of the molding process upon removal of thegating piece.

In one aspect, the molding apparatus includes opposed “A” and “B”surface mold tools each having front sides within which are formed oneor more article molding regions. The article molding regions of the “A”surface mold tool are aligned to mate with the article molding regionsof the “B” surface mold tool, such that when the mold tools are broughttogether, one or more closed molding cavities are formed within whichmolded articles are generated from a blended feed composition of apolymer and a filler. The article molding regions each generally have abody bounded by a perimeter that establishes an outer edge for thearticle molded in each of the closed molding cavities. Furthermore, thebody of each article molding region of the “A” surface mold tool isadapted for molding a bottom surface for the composite article, and thebody of each article molding region of the “B” surface mold tool isadapted for molding a top surface for the composite article. Adistribution channel is formed in at least the second surface mold tool,and has a main portion and a downstream terminus for each articlemolding region of the “A” surface mold tool. The main portion of thedistribution channel is formed outside of each article molding region.The downstream terminus, to which the main portion extends, is incommunication with the body of the respective article molding region ofthe “A” surface mold tool. This configuration facilitates the formationof a gating piece on the bottom surface of each molded composite articlewhile the outer edge of each article is free from attachment with thegating piece. Thus, when the gating piece is removed, the vestige isonly evident on the bottom surface of the article.

To facilitate removal of the molded composite article, the “A” surfacemold tool, in another aspect, is formed of a base and one or morelifters. A lifter is provided for each article molding region, and hasthe distribution channel formed therein so that the main portion of thechannel is hidden from the closed molding cavity and only the downstreamterminus is exposed to the cavity. After the article has been molded inthe closed molding cavity for a necessary period of time, the “A” and“B” surface mold tools separate, and each lifter is displaced away fromthe base to reveal the main portion of the distribution channel andexpose the gating piece so that the molded article and attached gatingpiece may be removed from the molding apparatus to a location where thegating piece may be separated from the finished article.

Additional advantages and features of the invention will be set forth inpart in a description which follows, and in part will become apparent tothose skilled in the art upon examination of the following, or may belearned by practice of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the accompanying drawings, which form a part of the specification andare to be read in conjunction therewith and in which like referencenumerals are employed to indicate like parts in the various views:

FIG. 1 is a perspective view of one embodiment of an “A” surface moldtool having article forming regions for forming the bottom surface ofmolded composite articles;

FIG. 2 is perspective view of one embodiment of the surface mold tool ofFIG. 1 with the lifters displaced from the base of the surface mold toolto reveal the distribution channel for delivering a blended feedcomposition to each article forming region;

FIG. 3 is a cross-sectional view taken along line 3-3 showing thepathway of the distribution channel in the lifters to reach adjacentarticle forming regions;

FIG. 4 is a perspective view of one embodiment of a “B” surface moldtool having article forming regions for forming the top surface ofmolded composite articles; and

FIG. 5 is a perspective view of a pair of molded composite articles andattached gating piece formed by the mating of the “A” surface mold tooland “B” surface mold tool to form the article forming regions intoclosed molding cavities.

DETAILED DESCRIPTION OF THE INVENTION

Illustrated in FIGS. 1 and 4 are an “A” surface mold tool 100 and a “B”surface mold tool 200, combining with one another to form a moldingapparatus for forming molded composite articles, such as compositebuilding products. The “A” surface mold tool 100 and “B” surface moldtool 200 have opposed front sides 102 and 202, respectively, that matewith one another in facing relation as the “A” tool 100 and “B” tool 200are brought together during a molding cycle. The front sides 102 and 202of the “A” tool 100 and “B” tool 200 surround article molding regions104 and 204, respectively. Each article molding region 104 of the “A”tool 100 combines with one article molding region 204 of the “B” tool200 when the front sides 102 and 202 are mating to form a closed moldingcavity where a blended feed composition is flowed to be molded into thefinished composite article. One exemplary set of composite articles, orbuilding products, formed by the “A” tool 100 and “B” tool 200 are shownin FIG. 5 in the form of composite shake shingles 300.

Each article molding region 104 of the “A” tool 100 has a body 106bounded by a perimeter 108. Likewise, each article molding region 204 ofthe “B” tool 200 has a body 206 bounded by a perimeter 208. When thefront sides 102 and 202 of the “A” tool 100 and “B” tool 200 are broughttogether, the perimeter 108 of one article molding region 104 of the “A”tool 100 mates with the perimeter 208 of one article molding region 204the “B” tool 200. In this way, the article molding regions 104 and 204are aligned with and facing one another in forming a closed moldingcavity. The body 106 of the “A” tool article molding region 104 and/orthe body 206 of the “B” tool article molding region 204 is recessed intothe respective tool front side 102 and/or 202. This recess allows thearticle molding region perimeters 108 and 208 to establish an outer orside edge 302 for each molded composite shake shingle 300 formed withinthe article molding regions 104 and 204. The article molding regions 104and 204 are designed, therefore, to set the shape and surfacecharacteristics of the molded shingle 300. More specifically, the body106 of the “A” tool article molding region 104 is configured to shapethe bottom surface 304 of the molded shingle 300, and the body 206 ofthe “B” tool article molding region 204 is configured to shape the topsurface 306 of the molded shingle 300. The exemplary “A” tool 100 and“B” tool 200 article molding regions 104 and 204, shown respectively inFIGS. 1 and 4, are designed to form shake shingles 300 with a specificsurface texturing. Therefore, each upper edge 110 of the article moldingregion perimeters 108 of the “A” tool 100 has a grooved pattern thatmates with a grooved pattern 210 of the opposed “B” tool 200 in order tocompletely seal the respective closed molding cavity formed by theopposed article forming regions 104 and 204. A grooved pattern 112matching the grooved pattern 210 of the “B” tool 200 may be continuedupwardly on the front side 102 from each upper edge 110 of the “A” tool100, in order to ensure a strong seal for the closed molding cavity.Additionally, a portion of the perimeter 108 and 208 surrounding eachbody 106 and 206 recessed into the respective tool front side 102 and202, for example, at upper edge 110 for the “A” tool 100, may betextured to form a portion of the shingle side edge 302 with acorresponding texture.

As can be seen in FIG. 5, the molded shingles 300 have a gating piece308 formed on the bottom surfaces 304 thereof as a by-product ofdelivering the blended feed composition to the article molding regions104 and 204. When the gating piece 308 is broken off at the interfacewith the shingle bottom surfaces 304, a vestige or mark is left behindas evidence of the molding process. Traditionally, this vestige ispresent on the side edge 302 of the molded article. Shake shingles, andother composite building products, are formed to replicate naturalproducts, such as wood shakes or boards, and marks that evidence amolding process and remain exposed after the molded article is installedon a structure are undesirable. Therefore, a distribution channel 400 isformed at least in the “A” tool 100 to deliver the blended feedcomposition to the body 106 of each article molding region 104, so thatany vestige is only present on the bottom surface 304 of the moldedshingle 300.

In the embodiment shown in FIGS. 1, 2 and 4, a port 214 is formed in thefront side 202 of the “B” tool 200 outside of the article moldingregions 204. The blended feed composition of at least a polymer (e.g., athermoplastic, a rubber, etc.) and a filler (e.g., limestone, woodfiber, etc.) is delivered from a location where the one or more polymersare melted to a liquid form and blended with the filler (along withother additives such as colorants, suitable UV inhibitors, lubricants,etc.) to create a composition that can exhibit fluid flowcharacteristics for delivery to each article molding region 104 throughthe distribution channel 400. For example, one manner of creating theblended feed composition to form each composite shingle 300 relies onthe use of a mixer and extruder. The raw ingredients for compositeshingle formation are mixed in the mixer (e.g., a kinetic mixer) andthen passed through the extruder. The mixture emerging from the extrudermay be sliced into small pellets by a rotary knife so that the materialcan be more easily conveyed through piping under air pressure or suctionto a storage location for use when needed (e.g., in a storage bin).Thereafter, the pellets are extracted from storage and fed a meltingchamber along with other additives to create the blended feedcomposition. The port 214 may alternatively be formed in the front side102 of the “A” tool 100 outside of the article molding regions 104. Ineither case, the distribution channel 400 in communication with the port214 is formed through a recess in either or both the front sides 102 and202 of the “A” tool 100 and “B” tool 200 outside of the respectivearticle molding regions 104 and 204. For instance, in the embodimentshown in FIGS. 1, 2 and 5, the distribution channel 400 is formed inboth the “A” Tool 100 and the “B” tool 200 through the mating contactbetween the respective front sides 102 and 202.

The specific pathway of the distribution channel 400, in one embodiment,is dictated by the implementation of lifters 114 in the “A” tool 100.The lifters 114 are positioned within a gap 116 formed between upper andlower base portions 118 and 120 of the “A” tool 100, and combine withthe lower base portion 120 to form the article molding regions 104. Theportion of each body 106 of the article molding region 104 where thedistribution channel 400 interfaces with the body 106 is formed by thelifter 114. Mating with a front face 122 of each lifter 114 when the “A”tool 100 and “B” tool 200 are brought together, such that the respectivearticle molding regions 104 and 204 form closed molding cavities, arerecess portions 216 in the front side 202 of the “B” tool 200.

With continued reference to FIGS. 1, 2 and 4, and with reference to FIG.3, the distribution channel 400 extends upwardly from the port 214 (orlocation opposite the port 214 on the “A” tool 100) to reach a lateralportion 402 of the channel 400. A divider 218 formed between the recessportions 216 mates with a recessed block 124 of the “A” tool 100 to formthe lateral portion 402 when the “A” tool and “B” tool front sides 102and 202 are brought together during the molding process. From thispoint, the channel lateral portion 402 extends in opposed directions andthen rearwardly along opposed sidewalls 126 of the lifters 114 to reachprimary channel portions 404 formed in the bottom surface 128 of thelifters 114. Continuing through the distribution channel 400, theprimary channel portions 404 each open through a neck 406 into adiverging channel portion, or downstream terminus 408, for the channel400. Each downstream terminus 408 opens directly into the body 106 ofthe respective article molding region 104 to deliver the blended feedcomposition into the closed molding cavity. In this orientation, theblended feed composition is molded within the distribution channel 400and the closed molding cavity formed by each set of opposed articlemolding regions 104 and 204 into the gating piece 308 and the compositeshingles 300, as seen in FIG. 5. The gating piece 308 is thereforeattached with the shingle bottom surfaces 304, and not the side edge 302or top surface 306 of the shingle 300. Preferably, the downstreamterminus 408 of the distribution channel 400 is spaced from theperimeter 108 of each article molding region 104, as can be seen inFIGS. 1 and 2.

Once a sufficient amount of time has passed for molded shingle 300curing within the closed molding cavities (e.g., under elevated heat andpressure), the front sides 102 and 202 of the “A” tool 100 and “B” tool200 are separated. The lifters 114, preferably hydraulically actuated,are moved out from the front side 102 of the “A” tool 100 and away fromthe upper and lower base portions 118 and 120 thereof to fully revealthe distribution channel 400 and gating piece 308 formed therein, asseen in FIG. 2. Hydraulic pins 126 extend from the body 106 of eacharticle molding region 104 to eject the molded shingles 300 from theregions 104 while suction arms or other robot arms (not shown) may use avacuum draw to capture the shingles 300 and move them to a locationwhere the gating piece 308 is separated from the shingles 300. Afterthis separation step, each molded shingle 300 is transported (e.g., by aconveyor) to a packaging location where multiple shingles 300 may bepackaged together for storage or shipment.

It can be seen, therefore, that the molding apparatus formed by the “A”surface mold tool 100 and a “B” surface mold tool 200 facilitates themolding of composite building products 300 where a gating piece 308 isformed on the bottom surface 304 of a molded article. Since certainchanges may be made in the above invention without departing from thescope hereof, it is intended that all matter contained in the abovedescription or shown in the accompanying drawing be interpreted asillustrative and not in a limiting sense. It is also to be understoodthat the following claims are to cover certain generic and specificfeatures described herein.

1. A method of molding a composite building product comprising:providing first and second surface mold tools, each of the first andsecond surface mold tools having a front side and at least one articlemolding region formed into the front side, wherein the second surfacemold tool is formed of a base and at least one lifter having a frontside, the second surface mold tool and the at least one liftercooperatively forming the at least one article molding region on thesecond surface mold tool, wherein each article molding region has a bodybounded by a perimeter that defines an outer edge for a molded compositebuilding product wherein the at least one lifter defines at least aportion of the perimeter, and wherein the body of each article moldingregion of the first surface mold tool is adapted for molding a topsurface for the composite building product and the body of each articlemolding region of the second surface mold tool and at least one lifterare adapted for molding a bottom surface for the composite buildingproduct when the surface mold tool and the second surface mold tool andthe at least one lifter are brought together in mating relation with thefront sides thereof contacting one another such that the respectivearticle molding regions thereof cooperatively form at least one closedmolding cavity within which at least one composite building producthaving an uninterrupted top surface is formed; providing a distributionchannel in at least the second surface mold tool, the distributionchannel having a main portion outside of the article molding regions ofthe first and second surface mold tools, and a downstream terminus incommunication with the body of the at least one article molding regionof the second surface mold tool, and wherein the at least one lifter hasa portion of the distribution channel formed therein, and wherein atleast one of the first and second surface mold tools includes a portoutside of each article molding region and in communication with thedistribution channel to deliver the flowing composition of a polymer anda filler to the distribution channel; positioning the first and secondsurface mold tools in mating relation with one another to form the atleast one closed molding cavity; flowing a blended composition of apolymer and a filler through the distribution channel and into the atleast one closed molding cavity; applying pressure to the blendedcomposition via flowably connected excess blended composition in saidport for a period of time sufficient to cure the blended compositionwithin each closed molding cavity into the composite building product;and separating the first and second surface mold tools to reveal one ormore molded composite building products; wherein the distributionchannel is adapted to form a gating piece on the bottom surface of eachcomposite building product with the outer edge of each compositebuilding product being free from attachment with the gating piece; andfor each closed molding cavity where a composite building product hasbeen molded, displacing each respective lifter away from the base andthe front side of the second surface mold tool to expose the gatingpiece and allow free removal of the composite building product.
 2. Themethod of claim 1, further comprising: removing the molded compositebuilding product under a vacuum draw; separating the gating piece fromthe bottom surface of the composite building product; and transportingthe molded composite building product to a location for packaging withother molded composite building products.
 3. The method of claim 1,wherein the terminus of the distribution channel is spaced from theperimeter of the at least one article molding region of the secondsurface mold tool.
 4. A method of molding a composite building productcomprising: providing first and second surface mold tools, each of thefirst and second surface mold tools having a front side and at least onearticle molding region formed into the front side, wherein the secondsurface mold tool is formed of a base and at least one lifter having afront side, the second surface mold tool and the at least one liftercooperatively forming the at least one article molding region on thesecond surface mold tool, and wherein each article molding region has abody bounded by a perimeter that defines an outer edge for a moldedcomposite building product wherein the at least one lifter defines atleast a portion of the perimeter, and wherein the body of each articlemolding region of the first surface mold tool is adapted for molding atop surface for the composite building product and the body of eacharticle molding region of the second surface mold tool and at least onelifter are adapted for molding a bottom surface for the compositebuilding product when the first surface mold tool and the second surfacemold tool and the at least one lifter are brought together in matingrelation with the front sides thereof contacting one another such thatthe respective article molding regions thereof cooperatively form atleast one closed molding cavity within which at least one compositebuilding product having an uninterrupted top surface is formed;providing a distribution channel in at least the second surface moldtool, the distribution channel having a main portion outside of thearticle molding regions of the first and second surface mold tools, anda downstream terminus in communication with the body of the at least onearticle molding region of the second surface mold tool, wherein the atleast one lifter has a portion of the distribution channel formedtherein, and wherein at least one of the first and second surface moldtools includes a port outside of each article molding region and incommunication with the distribution channel to deliver the flowingcomposition of a polymer and a filler to the distribution channel;positioning the first and second surface mold tools in mating relationwith one another to form the at least one closed molding cavity; flowinga blended composition of a polymer and a filler through the distributionchannel and into the at least one closed molding cavity; applyingpressure to the blended composition via flowably connected excessblended composition in said port for a period of time sufficient to curethe blended composition within each closed molding cavity into thecomposite building product; separating the first and second surface moldtools to reveal one or more molded composite building products; and foreach closed molding cavity where a composite building product has beenmolded, displacing each respective lifter away from the base and thefront side of the second surface mold tool to expose the gating pieceand allow free removal of the composite building product, wherein thedistribution channel is adapted to form a gating piece on the bottomsurface of each composite building product with the outer edge of eachcomposite building product being free from attachment with the gatingpiece, and wherein the terminus of the distribution channel is spacedfrom the perimeter of the at least one article molding region of thesecond surface mold tool.
 5. A method of molding a composite buildingproduct comprising: providing a first surface mold tool having a frontside and at least one article molding region formed into the front side,the article molding region of the first surface mold tool beingconfigured for molding an uninterrupted top surface of the buildingproduct and wherein the article molding region of the first surface moldtool includes a body defined by a perimeter that defines a top portionof an outer edge of the building product; providing a second surfacemold tool comprising a base having a front side and at least one lifterhaving a front side cooperatively forming at least one article moldingregion formed into the front side of the base and the lifter, thearticle molding region of the second surface mold tool being configuredfor molding a bottom surface of the building product and wherein thesecond surface mold tool includes a body defined by a perimeter whereinthe base and the lifter define the perimeter and bottom portion of theouter edge of the building product; bringing together in a matingrelation the front sides of the first surface molding tool, the base,and the lifter such that the front sides thereof contact one another toform at least one molding cavity within which at least one compositebuilding product having an uninterrupted top surface; providing adistribution channel formed in at least the base of the second surfacemold tool and in the at least one lifter, a main portion of thedistribution channel being in the base of the second surface mold tool,the main portion being in communication with a lifter portion of thedistribution channel formed within the at least one lifter, wherein atleast one of the first and second surface mold tools includes a portoutside of each article molding region and in communication with thedistribution channel to deliver the flowing composition of a polymer anda filler to the distribution channel, and wherein the distributionchannel has a termination proximate said lifter wherein said terminationis in communication with the at least one mold cavity, and wherein thelifter is adapted to form a gating piece on the bottom surface of eachcomposite building product wherein the outer edge of each compositebuilding product is free from attachment with the gating piece; flowinga blended composition of a polymer and a filler through the distributionchannel and into the at least one closed molding cavity; and separatingthe first and second surface mold tools to reveal one or more moldedcomposite building products having an uninterrupted top surface; anddisplacing the at least one lifter away from the base and the front sideof the second surface mold tool to expose the gating piece and allowfree removal of the composite building product.